Daily averages of SOHO/CELIAS/SEM disk integrated solar soft X-ray and
EUV flux measurements.
The SOHO Solar EUV Monitor (SEM) is a highly stable transmission grating
spectrometer that has made nearly continuous full disk solar irradiance
measurements since launch within an 8 nm bandpass centered at 30.4 nm, as well
as broadband solar soft X-ray and EUV flux measuremens in the spectral region
between 0.1 and 50 nm. It is this radiation from the Sun's hot corona that
controls the composition and dynamics of Earth's upper atmosphere. An increased
knowledge of the absolute solar flux and its variability in the EUV and X-ray
regions over a long time scale is therefore important for our understanding of
the solar-terrestrial connection.